The invention relates to a centrifugal pump.
A conventional centrifugal pump known in practice includes a distance disk installed therein with which the sealing clearance width between the pump impeller and the front wall region of the pump housing must be reset again after a certain operating time for reasons of wear in order to again increase the efficiency of the pump. This distance disk is seated on the pump shaft and on the one hand bears on its axial abutment and on the other hand on the rear wall of the pump impeller. In this manner, that is, with the help of the thickness of the distance disk, the axial position of the pump impeller on the pump shaft and thus the previously mentioned sealing clearance width is fixed.
If however the sealing clearance width has become too large, and specifically essentially on account of wear at the free axial blade sides of the pump impeller because the impeller has no front cover disk, then a complicated and time-consuming disassembly and reassembly of the impeller is necessary, wherein the pump housing must be opened very wide in order to exchange the mentioned distance disk for a thicker one or in order to place a further distance disk onto the pump shaft. In both cases the increase in thickness of the respective distance disk corresponds to the degree of wear.
The object of the invention lies in improving a centrifugal pump of the above mentioned type to the extent that the sealing clearance width between the front side of the pump impeller and the wall region of the pump housing, said wall region lying opposite this front side, may be adjusted after appearance of wear on the impeller front side and/or in the suction port region of the pump housing to the original value in a simple and quick manner.
A further object of the invention is the provision of a one-stage centrifugal pump on whose pump shaft, provided in the pump housing there is fastened a pump impeller which on the front side is free of a cover disk, wherein the pump shaft is provided with an axial abutment and a setting means which bears on this and which on the other hand engages on the pump impeller in order to set the sealing clearance width between the blades of the pump impeller and the wall region of the pump housing which lies opposite these blades, wherein the setting means is formed by a threaded ring seated loosely on the pump shaft and by a thread which is provided in the front hub region of the pump impeller and into which the thread of the threaded ring is screwed.
With this solution the mentioned sealing clearance width may again be set quickly and simply to its original width. Only the pressure piece, which in the usual manner with the help of the force of a screw axially screwed into the end of the pump shaft is pressed against the front side of the hub of the pump impeller, needs to be removed by releasing the screw. Thereafter the threaded ring used in place of the previously mentioned distance disk is rotated, whereupon the pump impeller is adjusted to the front, i.e. towards the central suction region. This has the result that the sealing clearance width is reduced again between the blades or the front cover disk of the pump impeller and the wall region, of the pump housing, which lies on the inside opposite these blades or this cover disk. Subsequently the mentioned pressure piece is again placed on and the screw is tightened in order to secure the new setting of the sealing clearance width. With this solution therefore the pump impeller does not need to be disassembled from the pump shaft since the threaded ring to be adjusted is accessible without further ado from the suction region of the pump housing after removal only of the mentioned pressure piece.
The suggested solution is particularly suitable for waste water pumps, and specifically for those which have a central and freely accessible suction region. The solution according to the invention is particularly advantageous with such waste water pumps when cutting means are provided in the central suction region which serves for the size reduction of larger solid matter in the medium being conveyed. Such cutting means apart from a stationary, annular cutting plate comprise a central rotating knife part which is fastened on the pump housing in place of the previously mentioned pressure piece and also assumes the function of the pressure piece. When using the cutting tool the pump impeller is subjected to a high wear on account of the solid matter in the conveyed medium so that the mentioned sealing clearance width increases more quickly. It is therefore necessary to again reset the sealing clearance in shorter time intervals. With this the gain in time with the resetting of the sealing clearance width is advantageously particularly noticeable on account of the solution according to the invention.
In an advantageous embodiment of the centrifugal pump according to the invention the thread of the threaded ring is designed as an outer thread and the thread in the front hub region of the pump impeller as an inner thread. This results in a simple design of the threaded ring. Furthermore it is advantageous for the two threads to be provided as fine threads by which means a very exact setting of the sealing clearance width between the impeller and the pump housing is possible.
Furthermore the threaded ring is secured in its axial position by way of a pressure body, wherein the pressure body presses the threaded ring against the axial abutment of the pump shaft and itself is screwed to the end of the pump shaft. The pressure body may furthermore be designed as a cutting means of a cutting tool provided in the suction region of the centrifugal pump.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.